When we go to restaurants and grocery stores, most of us assume that we’re getting what we pay for. But as a recent study shows, that’s not always the case—especially when it comes to seafood.

Seafood fraud is not a new issue, but according to a recently released study from Oceana, it continues to be a pervasive problem. From 2010 to 2012, Oceana conducted a seafood fraud investigation, collecting more than 1,200 seafood samples in 21 states. Using a DNA barcoding technique, a short DNA sequence was obtained from each sample and then compared to a catalogue of sequences from more than 8,000 fish species. This DNA testing showed that 33 percent of the samples analyzed were mislabeled, though there was tremendous variation depending on the type of fish purchased.

Red snapper in particular was the most commonly mislabeled—113 out of 120 samples were a fish species other than red snapper. Twenty-eight different species were substituted for red snapper, and 17 of those weren’t even in the snapper family at all. In one instance, the red snapper was actually tilefish, which the government advises sensitive groups to avoid due to high mercury levels.

Also raising health concerns, escolar was a substitute for white tuna in 84 percent of samples. Escolar is a snake mackerel that contains a naturally occurring toxin and can have serious digestive effects on people who eat more than a few ounces. The Food and Drug Administration actually advises against the sale of this species, and some countries have banned it outright. Consumers are not protected, though, when it’s mislabeled as white tuna.

There are many reasons that seafood fraud occurs. They include a lack of understanding, a desire to increase profits, and attempts to launder illegally harvested seafood. Somewhere along the supply chain, someone may substitute a lesser-valued fish. Others may short-weight the product, meaning the seafood processor misrepresents the weight of a seafood product so the customer gets less food for their money.

The consequences of this fraud are considerable. In addition to affecting human health when one species is swapped with another that may have contaminants, allergens, or toxins, seafood fraud disguises what is truly happening in the marketplace, incentivizing illegal fishing and threatening conservation efforts.

To address this critical issue, the SAFE Seafood Act was recently introduced to the House of Representatives and the Senate. This bill requires that seafood in the U.S. be traceable from its origin, standardizes seafood names, keeps illegally caught fish off the market, and increases inspections.

So what can you do to protect yourself from seafood fraud? Show curiosity about where your fish was caught and how. This will increase the dialogue around these important issues and hopefully encourage restaurants and stores to ask questions of their suppliers. Be knowledgeable about what you’re buying—and if the price seems too good to be true, it probably is.